System.gc() still resulting in garbage collections with -XX:+DisableExplicitGC

Y Srinivas Ramakrishna Y.S.Ramakrishna at Sun.COM
Mon Apr 14 12:00:07 PDT 2008


That is weird and unexpected (and could well be instrumentation error). Could you post a
snippet of the GC log (/var/log/jboss/gc.dat) showing a portion where such System.gc()'s may
be occurring?

-- ramki

----- Original Message -----
From: James Nichols <jamesnichols3 at gmail.com>
Date: Monday, April 14, 2008 11:31 am
Subject: System.gc() still resulting in garbage collections with -XX:+DisableExplicitGC
To: hotspot-gc-use at openjdk.java.net


> Hello,
> 
> I'm running with the following JVM arguments:
> 
>  -server -Xms4096m -Xmx4096m -XX:NewSize=1228M -XX:MaxNewSize=1228M
> -XX:MaxTenuringThreshold=4 -XX:SurvivorRatio=6 -XX:+ScavengeBeforeFullGC
> -XX:PermSize=256M -XX:MaxPermSize=256M -XX:-UseConcMarkSweepGC
> -XX:+UseParNewGC -XX:ParallelGCThreads=3 -XX:+CMSParallelRemarkEnabled
> -XX:+CMSClassUnloadingEnabled -XX:+CMSPermGenSweepingEnabled -verbosegc
> -XX:+DisableExplicitGC -XX:+PrintTenuringDistribution -XX:+PrintGCDetails
> -XX:+PrintGCTimeStamps -XX:+PrintHeapAtGC
> -XX:+PrintGCApplicationConcurrentTime -XX:+PrintGCApplicationStoppedTime
> -XX:+PrintClassHistogram -Xloggc:/var/log/jboss/gc.dat
> -Dsun.net.client.defaultConnectTimeout=10000
> 
> Using Jstat, I see a bunch of System.gc() calls showing up:
> 
> Timestamp         S0     S1     E      O      P     YGC     YGCT    FGC
> FGCT     GCT    LGCC                 GCC
>        189869.1   0.00   0.00   1.80  21.36  89.74   3109   15.401  3012
> 288.886  304.288 System.gc()          No GC
> 
> 
> Any ideas as to why I'm still getting these even though I have
> -XX:+DisableExplicitGC set?
> 
> Jim
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